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Filename Latest commit message Latest commit date
David Hildenbrand a5ddf2626d KVM: s390: vsie: fix some corner-cases when grabbing vsie pages
commit 5f230f41fdd9e799f43a699348dc572bca7159aa upstream.

We try to reuse the same vsie page when re-executing the vsie with a
given SCB address. The result is that we use the same shadow SCB --
residing in the vsie page -- and can avoid flushing the TLB when
re-running the vsie on a CPU.

So, when we allocate a fresh vsie page, or when we reuse a vsie page for
a different SCB address -- reusing the shadow SCB in different context --
we set ihcpu=0xffff to trigger the flush.

However, after we looked up the SCB address in the radix tree, but before
we grabbed the vsie page by raising the refcount to 2, someone could reuse
the vsie page for a different SCB address, adjusting page->index and the
radix tree. In that case, we would be reusing the vsie page with a
wrong page->index.

Another corner case is that we might set the SCB address for a vsie
page, but fail the insertion into the radix tree. Whoever would reuse
that page would remove the corresponding radix tree entry -- which might
now be a valid entry pointing at another page, resulting in the wrong
vsie page getting removed from the radix tree.

Let's handle such races better, by validating that the SCB address of a
vsie page didn't change after we grabbed it (not reuse for a different
SCB; the alternative would be performing another tree lookup), and by
setting the SCB address to invalid until the insertion in the tree
succeeded (SCB addresses are aligned to 512, so ULONG_MAX is invalid).

These scenarios are rare, the effects a bit unclear, and these issues were
only found by code inspection. Let's CC stable to be safe.

Fixes: a3508fbe9d ("KVM: s390: vsie: initial support for nested virtualization")
Cc: stable@vger.kernel.org
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Tested-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Message-ID: <20250107154344.1003072-2-david@redhat.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2025-03-13 12:43:07 +01:00
arch KVM: s390: vsie: fix some corner-cases when grabbing vsie pages 2025-03-13 12:43:07 +01:00
block partitions: ldm: remove the initial kernel-doc notation 2025-03-13 12:42:52 +01:00
certs
crypto crypto: pcrypt - Call crypto layer directly when padata_do_parallel() return -EBUSY 2024-12-14 19:44:23 +01:00
Documentation dt-bindings: mmc: controller: clarify the address-cells description 2025-03-13 12:42:53 +01:00
drivers leds: lp8860: Write full EEPROM, not only half of it 2025-03-13 12:43:06 +01:00
fs binfmt_flat: Fix integer overflow bug on 32 bit systems 2025-03-13 12:43:07 +01:00
include KVM: Explicitly verify target vCPU is online in kvm_get_vcpu() 2025-03-13 12:43:07 +01:00
init initramfs: avoid filename buffer overrun 2024-12-14 19:44:21 +01:00
ipc
kernel tasklet: Introduce new initialization API 2025-03-13 12:43:04 +01:00
lib lib: string_helpers: silence snprintf() output truncation warning 2024-12-14 19:44:39 +01:00
LICENSES
mm mm: vmscan: account for free pages to prevent infinite Loop in throttle_direct_reclaim() 2025-01-09 13:23:37 +01:00
net netem: Update sch->q.qlen before qdisc_tree_reduce_backlog() 2025-03-13 12:43:06 +01:00
samples samples/bpf: Fix a resource leak 2024-12-14 19:44:50 +01:00
scripts genksyms: fix memory leak when the same symbol is read from *.symref file 2025-03-13 12:43:00 +01:00
security tomoyo: don't emit warning in tomoyo_write_control() 2025-03-13 12:43:03 +01:00
sound ASoC: sun4i-spdif: Add clock multiplier settings 2025-03-13 12:42:55 +01:00
tools udp: gso: do not drop small packets when PMTU reduces 2025-03-13 12:43:06 +01:00
usr
virt KVM: arm64: Ignore PMCNTENSET_EL0 while checking for overflow status 2024-12-19 18:05:04 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore Remove *.orig pattern from .gitignore 2024-11-08 16:20:33 +01:00
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS
Makefile kbuild: userprogs: use correct lld when linking through clang 2025-03-13 12:43:04 +01:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.